Investigation of intermodal interference of LP01 and LP11 modes in the liquid-core optical fiber for temperature measurements

The intermodal interference of the LP₀₁ and LP₁₁ modes and determination of the equalization wavelength in the liquid-core optical fiber is presented. Theoretically was described the weakly guiding optical fiber with the constant core radius, where equalization wavelength is a function of the refractive indices of core and cladding. The dependence of equalization wavelength on refractive indices is employed for measurement of temperature. Temperature sensitivity using intermodal interference of modes LP₀₁ and LP₁₁ was documented in the liquid-core optical fiber consisted of fused silica as cladding and medicinal oil as a core. In the investigated temperature range the intermodal interference allows the temperature measurement with resolution of about 0.02 °C.